Electrical properties of BaTiO3nanoparticles in poly(ether imide)

The relative permittivity has been measured at audio frequencies and low temperatures for nanocomposites composed of poly(ether imide) (PEI) and BaTiO3 nanoparticles, the nanoparticles in a cavity and polycrystalline BaTiO3. The data at room temperature, for the real part of the relative permittivity versus nanoparticle content of the heat-treated nanocomposites, are found to follow a recently proposed modified Hanai equation. Also, a low-temperature relaxation region (in the vicinity of 20 K) is found in the heat-treated nanocomposites. This relaxation region is also observed in measurements on the nanoparticles packed in a cavity and for the polycrystalline BaTiO3 materials. A relaxation associated with water in the PEI is observed in the as-prepared nanocomposites. Finally, the breakdown strength of the heat-treated nanocomposites is found to decrease as the nanoparticle content increases. Microstructure-level simulations of electric field statistics were carried out and show that matrix field intensification cannot account for all of the variation of breakdown strength with nanoparticle concentration.